Really depends on budget and what kind of sound you want out of it (will probably depend on your setup). I personaly really love pure silver wire.
The main drawbacks are that it's solid core so it isn't very good for headphone cable, but I still have a pair of KSC75's recabled with 22AWG and although you gotta take special care of the wire, the sound is worth it.
Next I'd say look into Silver Plated Copper which is VERY cheap and sounds pretty good. It's stranded which works great for headphone wire and is readily available from navships on eBay, good guy, I always buy lots of wire from him.
Some people swear by Cardas cable, personally I haven't heard headphones recabled with Cardas, but my Cardas IPod Line Out has nothing on my pure Silver Line Out. Sure, the Cardas is warm and sounds good, but the Silver sounds cleaner and just has more detailed. I would definitly put Cardas as good though since I have a regular IPod Line Out (mini jack) and when using cheap copper / SPC interconnects, the Cardas does sound better.
The big thing to consider here is price.
Cardas 4x24 (4 23.5AWG cabled with thin blue jacket) is $6.75/ft from
www.partsconnexion.com
Silver 22AWG is $1.10/ft from
http://www.vt4c.com/shop/program/main.php (cheapest place, otherwise you're looking at around 3x that cost).
SPC is CHEAP! at around $10 / 50ft, eBay - navships.
Hope this helps with your decision, and know that for the most part, making DIY cables usually improves the sound over stock factory cables.